Arcane Missiles' trigger effect (the single pack of missiles) does not benefit from Magic Attunement and hence only has a range of 30 yds, whereas the channeling effect has a range of 36 yds. This can lead to a situation where the channeling effect is still maintained but no missiles are fired. As a result, Arcane Missiles seems not to fire at ranges comparable spells normally would do when already casting (I'd say app. 40 yds, although it could be more).

Capturing open PvP targets sometimes is not registered by the quest log.

At Crown Guard Tower in Eastern Plaguelands, standing in a specific range allows capturing of a tower, without actually giving credit for it. [Example]

At the Overlook in Hellfire, it is possible to not be registered by the PvP target (no bar appears), and when others cause the PvP target to be taken by your faction, you gain no credit. [Example 1] [Example 2]